1. Field of the Invention
The present invention relates to a charging device and an image forming apparatus.
2. Description of Related Art
A conventional electro-photographic image forming apparatus such as a printer, a copier, a fax machine, and a multifunction machine thereof forms an image through the following process. In a case of, for example, the printer, a surface of a photosensitive drum or an image supporting member is charged with a charging roller. Then, an LED head exposes the surface of the photosensitive drum to form a latent image. A developing roller electrostatically attaches a thin layer of toner to the latent image to form a toner image; and a transfer roller transfers the toner image to a sheet, thereby forming an image or printing. After transferring the toner image, a cleaning blade cleans toner remaining on the photosensitive drum. Afterward, the sheet with the toner image transferred thereon is sent to a fixing device, thereby fixing the toner image to the sheet.
When the printer with the above-described structure continuously performs the printing operation, the surface of the photosensitive drum may not be completely cleaned with a cleaning blade. In this case, remaining toner, exterior additive, sheet powder, and so on may adhere on the surface of the charging roller.
To solve this problem, it has been proposed to provide a charging device having a cleaning blade, so that toner, exterior additive, sheet powder and so on, which adhere onto the charging roller surface, can be scraped off.
However, in such a conventional charging device, when the cleaning member does not sufficiently scrape off toner, exterior additive, and so on due to a reduced size of toner particles or longer duration of the apparatus, toner, exterior additive, and so on adhering to the surface of the charging roller tend to form a film covering the surface. Accordingly, it is difficult to uniformly charge the photosensitive drum, thereby deteriorating image quality.
In view of the problems described above, an object of the invention is to provide a charging device and an image forming apparatus, which can uniformly charge an image supporting member and thereby can prevent quality loss, while solving the above problems of the conventional charging device.
Further objects and advantages of the invention will be apparent from the following description of the invention.